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ANEW SPECIES OF ZELTNERA (GENTIANACEAE) FROM MEXICO TAMAULIPAS, Turner Billie L. Plant Resources Center The University of Texas Austin, Texas 78712 ABSTRACT A new taxon, Zeltnera nesomii B.L. Turner, sp. nov., is described from the Sierra de San Z Carlos in Tamaulipas, Mexico. It is seemingly most closely related to the calycosa complex of northern Mexico and closely adjacent Texas but differs in numerous characters, including A ecogeography, brandling habit, and leaf, corolla, and anther size. photograph of the holotype is map provided, along with a comparing the distribution of the two species. KEY WORDS: Gentianaceae, Zeltnera, Z. calycosa, Mexico, Tamaulipas In Mansion's (2004* j>h\kti~ disme nb^ime.ii ul the wlassicjli ^>nc^r%ed Centaurium, the present novelty positioned in the predominantly North American genus Zeltnera. In his account, is because of its small anthers and corollas, Z. nesomii readily keys to or near Z. quitensis (Kunth) Mansion. But, as well noted by Broome (1976), the latter "is always easily recognized because of the small tetramerous flowers," a character not employed in Mansion's key to species. Zeltnera nesomii apparently belongs to Mansion's 'Texan group" of taxa, which includes 8 species, most of these treated by Turner (1993), albeit as part of Centaurium. Among these, Z. nesomii is seemingly most closely related to Z. calycosa (Buckl.) Mansion, The latter, however, has a larger, less intricately branched habit and larger floral parts and its geographic distribution and ecology Z New are distinct from the new species. The distribution of calycosa continues into Texas and Mexico. The two species are readily distinguished as follows. mm mm Larger cauline leaves 2-3 times as long as wide; corolla lobes 5-6 long, 2-3 wide; anthers, 1. mm before anthesis, ca 1.5 long Zeltnera nesomii mm mm Larger cauline leaves 3-5 times as long as wide; corolla lobes 8-11 long, 3-5 wide; anthers 1. mm ca 3 long before anthesis Zeltnera calycosa ZELTNERA NESOMII MEXICO. B.L. Turner, sp. nov. Figure TYPE: Tamaulipas. Mpio. San 1. N Carlos: Sierra de San Carlos, ca, 5 mi S of San Carlos, side of Bufa El Diente, igneous w bedrock, N-facing steep slope, roods of scattered oaks and shrubby vegetation of Rhus, Croton, Chiococca, Helietta, Vauquelinia, rich herbaceous layer, 770 m, 24° 31.5' N, 98° 57.6' W, flowers pink-rose, scattered but common, 17 Jun 1987, G. Nesom 6051 with J. Norris, M. Martinez, and L. Woodruff (holotype: TEX). Zeltnerae calycosae (Buckl.) Mansion similis sed differt foliis proximalibus 2-3plo longiorius mm mm quam 5-6 1-2 latioribus (vs 3-5plo), corollis minoribus (lobis in longitudine in latitudine vs mm mm 8-11 x 3-5 mm; tubis 8-9 in longitudine vs 10-12 mm), et antheris (preanthesis) minoribus mm (ca 1.5 in longitudine vs ca 3 mm). TEX). Figure Zeltnera nesom.il (holorype: 1. Annual glabrous herbs 10-15 cm tall, much-branched from about the middle of the main mm stem, the lower stems 4-sided arid possessing wings ca 0.25 wide. Leaves opposite below, elliptic to oblanceolate, mostly 1-2 an long, 0.5-1.0 cm wide, the margins entire. Inflorescence, much- mm 6-8 cm 6-8 cm 5-6 branched, terminal thryse ca high, wide. Corollas "pinkish-rose," the lobes mm mm mm mm long, 1-2 wide; tubes 8-9 long. Sepals 5, linear-lanceolate, 6-8 long. Anthers ca 1 mm long before anthesis, afterwards ca 1.5 long. Style;; ca as long as the stamens, broadly bilobed, mm mm mm their apices ca 0.25 wide. Capsules linear, 7-8 long, ca 1.5 wide. Seeds broadly ovate, mm mm ca 0.4 long, 0.3 wide. MEXICO. Additional specimen examined. Tamaulipas: Same locality as the Type but "near top of slope, igneous bedrock, open woods of scattered oaks and pines, ca 1200 m, scattered but n," 18 Jun 1987, Nesom 6140 (TEX). The novelty is named for Guy Nesom, collector of the plant on a field trip with colleagues from the University of Texas Plant Resources Center in 1 987. ACKNOWLEDGEMENTS My long-time colleague Guy Nesom kindly provided the Latin diagnosis and helpful comments. The dot map is based upon specimens on file at LL-TEX. LITERATURE CITED Broome, C.R. 1976. The Central American species of Centaurium (Gentianaceae). Brittonia 28: 413-126. A Mansion, G. 2004. new classification of the poiyphyletic genus Centaurium Hill (Chironiinae, Gentianaceae): Description of the New World endemic Zeltnera and reinstatement of Gyrandra Griseb. and Schenka Griseb. Taxon 53: 719-740. Turner, B.L. 1993. Texas species of Centaurium (Gentianaceae). Phytoiogia 75: 259-275. ZELTNERA • calycosa V o nesomii \ I e 2. Distribution of Zeltner northern Mexico.